This invention relates to a two-fluid nozzle for atomizing a liquid with a gas which includes a protector for the nozzle tip. In many applications, such as boilers, furnaces and coal gasification reactors, the harsh combustion environment unduly shortens nozzle life. The tip of the burner nozzle is most especially subjected to the greatest thermal stress. Thermal stress is defined as the mechanical force caused by expansion because of an increase in temperature of a body or portion thereof. Especially at areas of high thermal gradient, for example, at the discharge outlet where the atomized fluids exit the nozzle into the furnace or combustion zone and the geometry of the nozzle changes from contacting internal temperatures to contacting combustion zone temperatures over a very short physical distance, thermal stress can be very large. Chemical reactions in the combustion zone, i.e., formation of soot, slag or the like also greatly affect the tip. Mechanical erosion, for example by slurries, also presents nozzle throat and tip problems. Some industries accept this as a fact of life and plan for frequent nozzle changes. Others, in order to extend nozzle life have fabricated inserts of materials which are more resistant to the stresses encountered for parts that are subjected to the most stress. For example, Schlinger, U.S. Pat. No. 4,443,228, has added inserts of refractory material, such as tungsten carbide or silicon carbide to decrease mechanical erosion at the nozzle tip caused by slurries. Unfortunately, such materials are expensive, difficult to fashion into complex shapes and can nevertheless fail.
The present invention seeks to provide a nozzle which is highly efficient in atomizing the gas-liquid mixture, and which is more stable and durable to the various stresses of the harsh environment of use without changing the burner configuration greatly, or increasing the difficulty of manufacture by working with exotic ceramic or refractory materials.